A switching center is a facility that houses telecommunications equipment that couples, either directly or indirectly, to a feeder and distribution system that ultimately reaches homes and offices. A telephone line extends from a home or office, i.e., from a subscriber site, to a switching center. At the switching center, the line has traditionally been coupled to some form of switch, which, broadly speaking, is a unit of telecommunications equipment that is responsible for connecting telephone calls.
Today, telephone companies offer many telecommunications services. For example, a homeowner (subscriber) may wish to obtain access to a digital subscriber line (DSL) service, as well as having access to his or her traditional telephone service (POTS-plain old telephone service). Whereas historically all subscriber lines coupled to a POTS switch at a switching center, it is now necessary to couple a subscriber line to other units of telecommunications equipment, based upon the services desired by a subscriber. For example, a subscriber line that is intended to have access to DSL service as well as POTS service may be coupled to a multi-service access node (MSAN), while a subscriber line intended to provide only POTS service may be connected to a POTS switch.
To allow for various subscriber lines to couple to various units of telecommunications equipment, a selective coupling device may be employed toward the front-end of the switching center. The selective coupling device may possess many input ports to which subscriber lines couple, and may possess many output ports to which various units of telecommunications equipment couple. The selective coupling device couples a given subscriber line to a given unit of telecommunications equipment, in response to a command from a computer at the switching center.
The aforementioned scheme exhibits certain shortcomings. For example, to provide flexibility, the selective coupling device is often required to include many costly switching elements, thereby driving up the cost of such devices. Also, such devices have heretofore been “dumb” devices, meaning that they have needed to receive commands explicitly identifying which physical input port should be connected to which physical output port. Consequently, as the connections to, or between, the various selective coupling devices changes, the aforementioned telecommunications computer needs to be reprogrammed to accommodate such changes.